1. Field of the Invention
The present invention relates to a composite thin-film magnetic head comprising a recording head and a reproducing head and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
The performance of the reproducing head is improved by replacing the AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity. Alternatively, a pattern width such as an MR height, in particular, may be optimized. The MR height is the length (height) between an end of the MR element closer to the air bearing surface and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is a surface of the thin-film magnetic head facing toward a magnetic recording medium and may be called a track surface, too.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. One of the factors that determine the recording head performance is a pattern width such as a throat height (TH), in particular. The throat height is the length (height) of portions of magnetic pole layers facing each other with a recording gap layer in between, between the air-bearing-surface-side end and the other end. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface is reduced down to a submicron order. Semiconductor process techniques are utilized to implement such a structure.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of a thin-film magnetic head.
Reference is now made to FIG. 14A to FIG. 19A, FIG. 14B to FIG. 19B, and FIG. 20 to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 14A to FIG. 19A are cross sections each orthogonal to the air bearing surface of the thin-film magnetic head. FIG. 14B to FIG. 19B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 14A and FIG. 14B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, as shown in FIG. 15A and FIG. 15B, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR film having a thickness of tens of nanometers is formed for making an MR element 105 for reproduction. Next, on the MR film a photoresist pattern is selectively formed where the MR element 105 is to be formed. The photoresist pattern is formed into a shape that facilitates lift-off, such as a shape having a T-shaped cross section. Next, with the photoresist pattern as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element. Next, on the bottom shield gap film 104, a pair of electrode layers 106 are formed, using the photoresist pattern as a mask. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head. Next, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed.
Next, as shown in FIG. 16A and FIG. 16B, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 17A and FIG. 17B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 17B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 110), the recording gap layer 109, and part of the bottom pole layer 108 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of a magnetic flux generated during writing in a narrow track.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened. The polishing method may be mechanical polishing or chemical mechanical polishing (CMP). Through this polishing, the surfaces of the top pole tip 110 and the magnetic layer 119 are exposed.
Next, as shown in FIG. 18A and FIG. 18B, on the flattened insulating layer 111, a thin-film coil 112 of a first layer is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific pattern on the insulating layer 111 and the coil 112. Heat treatment is then performed to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a thin-film coil 114 of a second layer is then formed. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is then performed to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 19A and FIG. 19B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider is performed to form the air bearing surface 118 of the recording head and the reproducing head. The thin-film magnetic head is thus completed. FIG. 20 is a top view of the thin-film magnetic head. The overcoat layer 117 is omitted in FIG. 20.
In FIG. 19A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. In FIG. 19B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the recording track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 19A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coils covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle xcex8, and track width P2W as shown in FIG. 19A and FIG. 19B.
To achieve high surface recording density, that is, to fabricate a recording head with a narrow track structure, it has been particularly required that track width P2W fall within the submicron order of 1.0 xcexcm or less. It is therefore required to process the top pole into the submicron order through semiconductor process techniques. As the narrow track structure is obtained, it is also desired that the pole is made of a magnetic material having a high saturation flux density.
In Published Unexamined Japanese Patent Application Hei 7-262519 (1995) and in U. S. Pat. No. 5,606,478, for example, examples are disclosed, wherein a top pole layer or part of a bottom pole layer is made of a high saturation flux density material.
A problem is that it is difficult to form the top pole layer on the apex into small dimensions.
As disclosed in Published Unexamined Japanese Patent Application Hei 7-262519, for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or more. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a recording track width of the submicron order as described above, it is required to form a frame pattern of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine pattern of the submicron order through the use of a photoresist film having a thickness of 8 to 10 xcexcm or more. However, it is extremely difficult to form a photoresist pattern having such a thickness into a reduced pattern width, due to restrictions in a manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may be out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
As thus described, it is difficult in related art to fabricate the top pole layer with accuracy if the pole width of the submicron order is required.
To overcome the problems thus described, a method has been taken, as shown in the foregoing related-art manufacturing steps illustrated in FIG. 16A to FIG. 19A and FIG. 16B to FIG. 19B. In this method, a track width of 1.0 xcexcm or less is formed through the use of the top pole tip 110 effective for making a narrow track of the recording head. The top pole layer 116 to be a yoke portion connected to the top pole tip 110 is then fabricated (as disclosed in Published Unexamined Japanese Patent Application Sho 62-245509 [1987] and Published Unexamined Japanese Patent Application Sho 60-10409 [1985]). That is, the ordinary top pole layer is divided into the top pole tip 110 and the top pole layer 116 to be the yoke portion in this method. As a result, the top pole tip 110 that defines the track width is formed into a submicron width on the flat top surface of the recording gap layer 109.
However, the following problems are still found in such a thin-film magnetic head.
(1) In the related-art thin-film magnetic head shown in FIG. 19A and FIG. 19B, the track width of the recording head is defined by the top pole tip 110. Therefore, it is not necessary that the top pole layer 116 is processed into dimensions as small as those of the top pole tip 110. However, if the track width of the recording head is extremely reduced, that is, 0.5 xcexcm or less, in particular, processing accuracy for achieving the submicron order width is required for the top pole layer 116, too. However, the top pole layer 116 is formed on top of the apex in the related-art head. Therefore, it is difficult to reduce the top pole layer 116 in size, due to the reason described above. In addition, the top pole layer 116 is required to be greater than the top pole tip 110 in width since the top pole layer 116 is required to be magnetically connected to the top pole tip 110 smaller in width. Because of these reasons, the top pole layer 116 is greater than the top pole tip 110 in width in the related-art head. As a result, writing may be performed on a side of the top pole layer 116 and so-called xe2x80x98side writexe2x80x99 may results, that is, data is written in a region of a recording medium where data is not supposed to be written. Such a problem more frequently results when the coil is two-layer or three-layer to improve the performance of the recording head and the apex is thereby increased in height, compared to the case where the coil is one-layer.
(2) In the related-art magnetic head, the throat height is defined by the end of the top pole tip 110 opposite to the air bearing surface 118. However, if the top pole tip 110 is reduced in width, edges of the pattern are rounded in a photolithography process. As a result, the throat height that is required to be precisely controlled is made uneven, and the balance between the throat height and the track width of the MR element is disturbed in the steps of lapping the air bearing surface 118. For example, if the track width of 0.5 to 0.6 xcexcm is required, the end of the top pole tip 110 opposite to the air bearing surface 118 may be shifted from the zero throat height position (that is, the position of the air-bearing-surface-side end of the insulating layer that defines the throat height) toward the air bearing surface 118. The recording gap is thus made greater and writing of data is made impossible.
Due to the problems (1) and (2) thus described, it is difficult to reduce the track width of the recording head of the related-art thin-film magnetic head.
(3) Furthermore, in the related-art magnetic head, it is difficult to reduce the magnetic path (yoke) length. That is, if the coil pitch is reduced, a head with a reduced yoke length is achieved and a recording head having an excellent high frequency characteristic is achieved, in particular. However, if the coil pitch is reduced to the limit, the distance between the zero throat height position and the outermost end of the coil is a major factor that prevents a reduction in yoke length. Since the yoke length of a two-layer coil can be shorter than that of a single-layer coil, a two-layer coil is adopted to many of recording heads for high frequency application. However, in the related-art magnetic head, a photoresist film having a thickness of about 2 xcexcm is formed to provide an insulating film between coil layers after a first layer is formed. Consequently, a small and rounded apex is formed at the outermost end of the first layer of the coil. A second layer of the coil is then formed on the apex. The second layer is required to be formed on a flat portion since it is impossible to etch the seed layer of the coil in the sloped portion of the apex, and the coil is thereby shorted.
Therefore, if the total coil thickness is 2 to 3 xcexcm, the thickness of the insulating film between the layers of the coil is 2 xcexcm, and the apex angle is 45 to 55 degrees, for example, the yoke length is required to be 8 to 10 xcexcm which is twice as long as the distance between the outermost end of the coil and the neighborhood of the zero throat height position, that is, 4 to 5 xcexcm (the distance between the innermost end of the coil and the portion where the top and bottom pole layers are connected to each other is required to be 4 to 5 xcexcm, too), in addition to the length of the portion corresponding to the coil. This length of the portion other than the portion corresponding to the coil is one of the factors that prevent a reduction in yoke length.
Assuming that a two-layer eleven-turn coil whose line width is 1.0 xcexcm and the space is 1.0 xcexcm is fabricated, for example, the portion of the yoke length corresponding to the coil 112 of the first layer is 11 xcexcm, if the first layer is made up of six turns and the second layer is made up of 5 turns, as shown in FIG. 19A and FIG. 19B. In addition to this length, the total of 8 to 10 xcexcm, that is, the distance between each of the outermost and innermost ends of the coil 112 of the first layer and each of ends of the photoresist layer 113 for insulating the coil 112, is required for the yoke length. In the present invention, the yoke length is the length of a portion of the pole layer except the pole portion and the contact portions as indicated with L0 in FIG. 19A and FIG. 19B. In the related art it is impossible to further reduce the yoke length, which prevents improvements in high frequency characteristic.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for reducing a track width of a recording head and reducing a yoke length.
A thin-film magnetic head of the invention comprises: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located in regions on a side of a medium facing surface of the head that faces toward a recording medium being opposed to each other, the magnetoresistive element being placed between the portions of the shield layers; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The first magnetic layer is located next to the reproducing head and includes: a first portion located in a region including a region that faces the coil; a second portion forming one of the pole portions and connected to a surface of the first portion facing the coil; and an auxiliary layer made of a high saturation flux density material and located at least between the first portion and the at least part of the coil, the auxiliary layer forming part of a magnetic path. The at least part of the coil is located on a side of the second portion of the first magnetic layer.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located in regions on a side of a medium facing surface of the head that faces toward a recording medium being opposed to each other, the magnetoresistive element being placed between the portions of the shield layers; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The first magnetic layer is located next to the reproducing head. The method includes the steps of: forming the reproducing head; forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the coil such that the at least part of the coil is insulated from the first and second magnetic layers. The step of forming the first magnetic layer includes formation of: a first portion located in a region including a region that faces the coil; a second portion forming one of the pole portions and connected to a surface of the first portion facing the coil; and an auxiliary layer made of a high saturation flux density material and located at least between the first portion and the at least part of the coil, the auxiliary layer forming part of a magnetic path. In the step of forming the coil, the at least part of the coil is formed on the auxiliary layer such that the at least part of the coil is placed on a side of the second portion of the first magnetic layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the first magnetic layer is provided. The first magnetic layer includes: the first portion located in a region including a region that faces the thin-film coil; and the second portion forming the pole portion and connected to a surface of the first portion facing the coil. At least part of the coil is placed on a side of the second portion of the first magnetic layer. As a result, the second magnetic layer of the recording head is formed on the flat surface. The track width of the recording head is thereby reduced. Furthermore, according to the invention, the auxiliary layer made of a high saturation flux density material is provided at least between the first portion of the first magnetic layer and at least part of the coil. The auxiliary layer forms part of the magnetic path. As a result, the total thickness of the first portion and the auxiliary layer is reduced and it is thereby possible to increase the thickness of the coil. It is therefore possible to reduce the line width of the coil. As a result, a reduction in yoke length of the recording head is achieved.
In the present invention the high saturation flux density material is a magnetic material having saturation flux density of 1.4 T or greater.
According to the thin-film magnetic head or the method of the invention, the second portion of the first magnetic layer may define a throat height, and the second magnetic layer may define a recording track width.
According to the head or the method, the second magnetic layer may include: a magnetic pole portion layer forming one of the pole portions; and a yoke portion layer connected to the pole portion layer and forming a yoke portion. In this case, the thin-film coil may include a first layer portion located on a side of the second portion of the first magnetic layer and a second layer portion located on a side of the pole portion layer of the second magnetic layer. In this case, the pole portion layer of the second magnetic layer may be equal to or greater than the second portion of the first magnetic layer in length. An end face of the yoke portion layer that faces toward the recording medium may be located at a distance from the medium facing surface of the head.
According to the head or the method, the auxiliary layer may cover the first and second portions of the first magnetic layer.
According to the head or the method, the second portion of the first magnetic layer may be made of a high saturation flux density material.
According to the head or the method, an insulating layer may be further provided. The insulating layer covers at least part of the coil located on the side of the second portion of the first magnetic layer, a surface of the insulating layer that faces the recording gap layer being flattened. In this case, the second portion of the first magnetic layer may surround at least part of the coil.
According to the head or the method, the first magnetic layer may function as the second shield layer, too.
Other and further objects, features and advantages of the invention will appear more fully from the following description.